


Mendelian Inheritance

by PostcardsfromTheoryland



Series: The Little Things Are Infinitely the Most Important [3]
Category: Sherlock (TV)
Genre: Christmas, Parentlock, sort of
Language: English
Status: Completed
Published: 2013-12-25
Updated: 2013-12-25
Packaged: 2018-01-06 02:00:19
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,725
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1101070
Author URL: https://archiveofourown.org/users/PostcardsfromTheoryland/pseuds/PostcardsfromTheoryland
Summary: <blockquote class="userstuff">
              <p>The morning of December 24th found 221B quiet and peaceful in a way it could only be after a grueling case – with both of its occupants dead to the world.  Which is why it was odd that John woke up to the sound of a baby crying.</p>
            </blockquote>





	Mendelian Inheritance

**Author's Note:**

  * For [Meggs (SweetieOolong)](https://archiveofourown.org/users/SweetieOolong/gifts).



> Written as part of the letswritesherlock winter ficlet challenge, prompt 2 - Gift giving.  
> This is also a Christmas gift for my dear beta. Thank you for being the John to my Sherlock.

The morning of December 24th found 221B quiet and peaceful in a way it could only be after a grueling case – with both of its occupants dead to the world. Remnants of dim sum, fried rice, and sweet and sour chicken littered the kitchen table, fighting for space with a half-completed experiment testing the toxicity levels of shellfish. John lay fast asleep, curled awkwardly on the sofa in a way that would make his shoulder throb upon waking. His bed, infinitely more comfortable, was simply too far away. Sherlock hadn’t even made it onto a soft surface, instead sprawled on the floor in front of the now cold hearth. Any minute now Mrs. Hudson would pop in, wake them up for a full breakfast, remind them that she was most certainly not their housekeeper, and life would continue as usual.

Which is why it was odd that John woke up to the sound of a baby crying.

He thought it was the lingerings of a strange dream, at first. Sherlock hadn’t so much as twitched, and wouldn’t Mrs. Hudson have mentioned something if she was planning on babysitting? Always better to be cautious whenever Sherlock Holmes was involved. So, it must have been his imagination, then. John fluffed the pillow and pulled his blanket back up, intent on making the most of this ideal sleeping environment.

The baby cried again.

“Sherlock, did you hear that?”

“…was the baker, Lestrade….” came the mumbled response. It took John an embarrassing amount of time to convince himself that neither a baker nor Greg Lestrade would be crying like a baby at their door.

“What?”

“Baker…killed the old woman. There’s…poison…in the cake.”

Right. Sherlock was deducing in his sleep. Of course he was.

“No, Sherlock. There’s a baby. Wake up.”

“Wasn’t any baby at…scene, Lestrade.” This was getting them nowhere. John forced himself off of the sofa and padded over to open the door. He wasn’t hearing things, then. There was a basket on the landing, complete with a teary-eyed baby wrapped snuggly in a soft green blanket and looking up at him forlornly. There was a bag off to the side, holding what looked like several cans of formula and a few cloth diapers. John’s first instinct was that this was a mistake or some random prank until he noticed the paper taped to the side of the basket, folded neatly so that a single word was visible: “Sherlock.” John closed the door briefly; maybe when he opened it again the baby would be gone and he could focus his attention on yelling at his flatmate for putting hallucinogens in his tea last night.

It was still there, now smiling and giggling at him and John realised he was, in effect, playing peek-a-boo with a strange baby on their landing and it was far too early in the morning for this. He closed the door a second time (it might be a strange baby on their landing but he should still avoid raising his voice in front of it) and turned to his flatmate.

“Sherlock, what the _hell_ have you done?” Said man on the floor finally roused a bit and blinked blearily at him.

“I haven’t done anything,” he grumbled. “Oh, and the fire’s out.”

“There’s a baby, Sherlock. There’s a baby on our landing.”

“Well, I didn’t put it there.”

“Sherlock,” John ground out. “A little help figuring out exactly why someone thought we needed a baby?” Sherlock sighed dramatically and made a vague wave in his general direction.

“Bring it inside, then.” John did as he was told, fetching the basket and setting it right next to Sherlock’s head.

“Here. Deduce.”

“You’re right. It’s a baby,” he said flatly, turning over and scooting closer to the nonexistent fire.

“For God’s sake,” John sighed. The infant hadn’t seemed especially happy in that basket, so John plucked it out and carried it into the kitchen while he read the accompanying note. He only managed to make it through the first sentence, however, before he stopped dead in his tracks. “Sherlock, this is important.”

“I fail to see how the baby erroneously left on our stoop impacts me.”

“There’s a note. Someone’s saying this is your son.” _That_ got a reaction. Sherlock scrambled upright, still not completely in control of his limbs as he slid to a stop in front of them, scrutinizing the infant and then the letter. “Isn’t this when you tell me the note is clearly a lie because you’re certainly not interested in that sort of thing?” Sherlock looked up from his inspection with a raised eyebrow. “You – you’re not, though, are you?"

“Doesn’t sound like me, does it?”

“You didn’t actually answer the question, you know.” Sherlock pointedly ignored him for several minutes before finally stepping back and clearing his throat awkwardly.

“Exactly how old would you say that thing is?” John decided to temporarily overlook the fact that Sherlock was referring to the baby as a “thing” and began his own examination.

“Considering that he can lift his head up and is responding fairly well to voices, I’d say, maybe about four months, give or take? Why?” But even as he asked the question, the math started falling into place in his head. Four months, plus the nine for gestation put conception at about a little over a year ago. And Sherlock had only been back in London for six months. There were still gaping holes, large swatches of time that John didn’t know what the man had been doing, but there was no way settling down to have a baby would be on the agenda – would it? He looked down at the baby again, noticing the blue eyes for the first time. That didn’t necessarily mean anything, though. Lots of babies had blue eyes.

“There is a distinct possibility that this baby might indeed be mine.” John didn’t know how to respond to that, so he settled for staring at Sherlock for a good five minutes. The baby, who was apparently possibly Sherlock’s son, spent the time reaching up and attempting to tug on John’s ears.

“You had…sex, then. With a woman. While you were…abroad,” he finished lamely. Sherlock was very astutely facing the other direction.

“Yes. Once.”

“You didn’t use, um, protection, then?”

“No, she,” Sherlock cleared his throat again, “she assured me she was taking contraceptives.”

“You’re sure this is your son, then?”

“No, not entirely. I’d need to run paternity tests. But it’s incredibly probable.”

“Right. Of course. Right.” This was getting out of hand very quickly. “Dare I ask who his mother is?”

“Irene.”

“Irene Adler?! Sherlock, Irene Adler is dead!”

“Really,” he replied blandly. “And here I thought she’d got into a witness protection program in America.” John grimaced.

“Yes, alright, fine, I apologise for that but – wait.” Sherlock blinked innocently at him. “You didn’t. I would have noticed you running off to Karachi.”

“You conveniently spent the week at your sister’s trying to get her sober. Ineffectually, I might add.”

“Not the time.” Sherlock blessedly took the hint, but now the baby was beginning to fuss. He might be hungry. “Does that note mention anything about the last time he was fed? Or his name, for that matter?” Sherlock’s mouth turned up in a bit of a smirk at that.

“Hamish.”

“You’re joking.”

“I’m not, actually,” he chuckled. “And no, nothing about feeding.”

“Right then. I suppose heating up some formula won’t be too much trouble. But we need to talk about this, Sherlock. You’ve – probably – got a son. This is going to be a big change. Sherlock?” John turned to see the detective was already doing up his scarf and collecting his coat from where he’d let it fall in a heap the night before.

“Call Mycroft. Have him send the child…somewhere. Away. A home.”

“Where are you going?”

“Out,” Sherlock growled, the door slamming behind him with a definitive finality that made the baby – Hamish – that made Hamish flinch in his arms. Well then.

Hamish predictably started crying in earnest after the dramatic exit, but it was easily remedied with a bit of formula. Irene had thoughtfully left a bottle in the bag - clearly she’d understood exactly how paternal Sherlock Holmes might be because the accompanying instructions were addressed to John. With Hamish happily fed, John set about making himself some toast with jam, hardly noticing that he’d settled himself in front of the telly with Hamish still in his arms. The boy looked entranced by the pictures on the screen and John realised he was deliberately hesitating to call Mycroft. It wasn’t as if the man didn’t already know, anyways. There wasn’t any harm in letting Hamish stay at 221B for a bit, at least until Mycroft stopped overtaking small countries long enough to grant them a visit.

* * *

Mycroft was in the flat by the time Sherlock crept back up the stairs, speaking with John in low murmurs. Sherlock’s immediate assumption was that they hadn’t wanted him to hear the conversation, but a second glance showed it was for the baby’s benefit – cozily asleep in John’s arms.

An image, unbidden, suddenly appeared in his head – several years in the future, Sherlock examining something at the kitchen table while a small boy of maybe seven years with curly dark hair was sitting on the stool next to him, asking why he’d chosen that particular set of variables. And then a second, a crime scene with a gangly teenager explaining to Sherlock why he’d been wrong about the bruising patterns on the victim’s torso, a third of him playing violin duets with that same teenager.

No, this was foolish. He had neither the life nor the desire for a child. He was a consulting detective, regularly injured during cases, there was admittedly a period of his life during which he was addicted to cocaine, and there were frequently more body parts in the kitchen than there were food items.

And yet, seeing John and Hamish like that, natural, as if Hamish had always been here – there was something about it that made Sherlock doubt whether sending the child away would be the best course of action.

“Wait.” John turned to him in surprise while Mycroft simply sent a glance in his direction.

“Good of you to join us at last, Sherlock. Ms. Adler’s note implied that she would be coming to reclaim Hamish when she was able, but in the meantime we’ll be sending him to the best orphanage in the country.”

“No.” His brother raised an unimpressed eyebrow.

“No? I understand the connotations, but do you really imagine I would deign to send my nephew someplace that he wouldn’t be receiving the best care possible?”

“I said no. Hamish is staying here.”

“He’s what?” This time it was John staring at him in shock. “Three hours ago Hamish was a ‘thing’ that was ‘possibly’ your son and now all of a sudden he’s staying here?”

“Don’t be ridiculous, John, of course he is. It’s clear Hamish is quite taken with you already, and it’s just not statistically plausible that an orphanage, with a generally 10:1 child to adult ratio in the best of circumstances, could provide better care than we could.”

“This is unwise, Sherlock,” Mycroft murmured. “You’re making a mistake.”

“That’s your opinion,” Sherlock snidely informed him. “Oh, and we’ll need the essentials sent over here. Whatever it is that new babies need.” John gave an exasperated sigh.

“I’ll text you a list, Mycroft.” The man stared at them both in shock and left without another word. John looked up at Sherlock, Hamish still fast asleep, and began helplessly laughing. “We’re raising a baby, then?”

It was then that Sherlock realised John hadn’t said anything about wanting to raise Hamish with him. Sherlock panicked – perhaps he’d been presumptuous. What if John didn’t actually want anything to do with Hamish? God how was he going to raise a baby on his own?

“Is this alright? I could, ah, start looking for a new flat if this isn’t…”

“If you think,” John interrupted him, “for one second, that I’m going to let you attempt to raise a child on your own, you are more of an idiot than I thought you were.” Sherlock relaxed with smile, almost collapsing onto the couch. John joined him a few seconds later and attempted to carefully hand Hamish off to him. Sherlock immediately backed away, terrified by the proposition. “Oi, come on. You just agreed to be a proper parent, the least you could do is actually hold your son.”

“I’ll still need to run the paternity test.”

“Of course. Now take the baby.” Sherlock reached timidly for him, half expecting the infant to snap awake and start crying at the change. He didn’t, though – merely snuggled a bit against Sherlock’s chest and was content to drop off again. It was – surprisingly pleasant.

“Magadan.”

“You’re what?”

“We were in Magadan. Port town on the northeastern coast of Russia. One of the last parts of Moriarty’s organisation, smuggling ring, was stationed there, God knows why. Only it gets quite cold in the winter months and I was – well, I was broke and I’d lost contact with Mycroft. In the midst of trying to figure out how exactly I was going to survive on the streets in freezing temperatures, Irene approached me. She had several clients in the mining industry in the area, and she made me a deal: I could stay at her ridiculously posh mansion of a house, but at the end I had to give her a night of my time. I wasn’t really in a position to turn down the offer.”

“And that’s when…” John trailed off and glanced down at the sleeping child in Sherlock’s arms.

“Presumably, yes.” John hummed in response.

“Interesting how these things work out, isn’t it?” Hamish chose that moment to come awake with a wail and Sherlock startled, turning to John in distress.

“What’s wrong? What did I do?”

“You didn’t do anything, Sherlock,” John laughed. “He’s probably just hungry again. Or he might need to be changed.” The look of terror grew.

“He needs what?” John seemed to take pity on him, scooping Hamish out of Sherlock’s arms and heading into the kitchen.

“I’m letting you off the hook, just this once, but I expect you to watch closely. You’re a genius; don’t try to tell me you can’t figure out how to fix up some formula and change a nappy.”

“Wouldn’t dream of it.”

“Oh, and Sherlock,” John called over Hamish’s growing cries. “Happy Christmas Eve. My gift is going to look tame now that Irene’s sent over a baby.”

“I assume you mean the container of salicylic acid in the bottom of your wardrobe? Which was quite thoughtful, by the way. I’m sure Hamish and I will enjoy testing its properties.” John looked up from the bottle he was heating in panic.

“You are _not_ doing experiments with Hamish.”

“What? Why not? I thought he’d like it.”

“Sherlock. He’s a baby. You do not perform experiments with the baby.” But as soon as the words were out of his mouth he realised it was a mistake because now there was a calculating glint in Sherlock’s eyes.

“Which presumably means that I can perform experiments with Hamish at some point in the future when he is not a baby. Is there a specific milestone at which he ceases to be referred to as a ‘baby’ and begins to be simply a ‘child?’ And what exactly qualifies as an experiment?”

“We are not having this discussion now.”

“And are the parametres affected by the amount of protective equipment involved?” he carried on. “There needs to be some sort of chart accounting for all the variables.”

“Yes, right, you do that. Later. Here.” And with that John shoved the infant, bottle and all, back in Sherlock’s arms. Hamish looked up at him warily, somewhat concerned that he wasn’t John but placated by the fact that he was being fed. Then John set about disinfecting the kitchen, grumbling about pig blood stains, while Sherlock began thinking up a list of potential non-dangerous experiments to try as soon as Hamish could understand them.

This parenting lark was going to be a piece of cake.


End file.
